Gerardo Gutierrez-Juarez

• University of Guanajuato

The Photoacoustic (PA) effect is the mechanism to convert non-ionizing electromagnetic energy into mechanical one; its main application is PA imaging in biomedicine. In this work, and in order to consider the heat flux non-heuristically, we obtained exact solutions of a 1D boundary value problem of the Dual-Phase-Lag (DPL) heat conduction equation...

Acoustic emission from the compounds [Fe(HB(tz)3)2] and [Fe(Htrz)(trz)2]BF4 was detected during the thermally induced spin transition and is correlated with simultaneously recorded calorimetric signals. We ascribe this phenomenon to elastic waves produced by microstructural and volume changes accompanying the spin transition. Despite the perfect re...

Introduction In this study, we utilized the pulsed photoacoustic (PA) technique to analyze globular sedimentation in whole human blood, with a focus on distinguishing between healthy individuals and those with hemolytic anemia. Methods Blood samples were collected from both healthy individuals (women and men) and those with hemolytic anemia, and t...

A new piecewise function to determine the thickness profile of transparent thin films, is built from a piecewise scaled function of the 1D gray value plot obtained through monochromatic-light-interferometry. In the gray value piecewise function each subfunction contains the information of the physical phenomena related to fringe pattern formation a...

A new approach based on a variant of differential photoacoustic (PA) cells, and a first-order approximation of RG model, is used to measure directly the thermal effusivity in solids is proposed. The configuration consists of two identical conventional photoacoustic cells, in both, the system is gas-sample-backing. In one of them, the backing works...

This work contributes to the development of microfluidics devices in a simpler way and by keeping the cost of microfabrication as low as possible. Implementing methods to develop microfluidic devices and to have control over the channel size rapidly and easily have become a challenge. In the present work, direct laser writing (DLW) is proposed as a...

Polymeric cylindrical micro-pedestals were fabricated using a low-cost direct laser writing system. These were coated with Rhodamine 6G dye to allow lasing action. Microlasers, exhibit Whispering Gallery Modes with Q ≥ 2000 and a lasing threshold ≤ 5 µJcm – ² .

A method based on a generalized function in Fourier space gives analytical solutions to homogeneous partial differential equations with constant coefficients of any order in any number of dimensions. The method exploits well-known properties of the Dirac delta, reducing the differential mathematical problem into the factorization of an algebraic ex...

En este trabajo presentamos la fabricación de nanopartículas de plata (Ag-NPs) por medio de ablación láser (AL) en medio acuoso, y su aplicación como elementos de realce de señales Raman a través de procesos tipo SERS. Esta metodología permite obtener suspensiones estables de NPs libres del uso de procesos químicos, con dispersiones de tamaños rela...

In this study, a dual pulsed photoacoustic technique was applied to monitor, in real time, the laser ablation synthesis in solution (LASiS) of silver nanoparticles. It was found that, at low optical fluence values, the ultrasound signal associated to the laser ablation process exhibited constant amplitude, independently of the ablation time. Furthe...

The behavior of the photoacoustic signal produced by nanoparticles as a function of their concentration was studied in detail. As the concentration of nanoparticles is increased in a sample, the peak-to-peak photoacoustic amplitude increases linearly up to a certain value, after which an asymptotic saturated behavior is observed. To elucidate the m...

Behavior of the photoacoustic signal produced by nanoparticles as a function of their concentration was studied in detail. As the concentration of nanoparticles is increased in a sample, the peak-to-peak photoacoustic amplitude increases linearly up to a certain value, after which an asymptotic saturated behavior is observed. These concentration-de...

We model theoretically the voltage response to an acoustic pulse of a multilayer system forming a low noise capacitive sensor including a Polyvinylidene Fluoride piezoelectric film. First we model a generic piezoelectricdetector consisting of a piezoelectric film between two metallic electrodes that are the responsible to convert the acoustic signa...

It is widely held that the melanosome is an exemplar of the absorption features of melanin-containing cells, which are assumed to be uniform in both size and optical characteristics. In recent years, however, it has become increasingly apparent that this is a strikingly poor assumption. Indeed, melanin extracted from natural sources and synthetic m...

A comparative study of the optical properties of organic fluorescent nanoparticles fabricated by laser ablation (NPs-LA), reprecipitation (NPs-RP), and microemulsion (NPs-ME) methods is presented. These nanoparticles contain a fluorene-based p-conjugated molecule (BT2). Distinctive electronic transitions are observed in samples due to the specific...

Encouraged to improve the procedure to measure the blood flow in cases with peripheral artery disease using thermography, that allows to evaluate several arteries simultaneously, it was developed an alternative to measure the volumetric flow through a conduit, it was studied the variation of the thermal energy computed from thermal images due to ch...

Usually organic nanoparticles (o-NPs) are synthesized by reprecipitation/microemulsion methods. In this work, o-NPs intended for two-photon fluorescent microscopy were synthesized using reprecipitation and laser ablation methods. A comparative study of their optical properties is presented.

Nanoparticle-assisted ultrasound generation by pulsed laser or photoacoustic (PA) techniques has been employed in the study of several tissues both in vivo and in vitro. Among the many applications of this technology, the detection of few cells in vitro is of particular interest. However, the toxicity induced by laser irradiation used for PA signal...

The influence of size, geometry, temporal response of finite sensors and source geometry on the detected photoacoustic pressure is explored. We started considering the transducer simulated by a mesh of point-like sensors connected in parallel, which implies that appropriate modeling of pressure depends on the discretization size of the sensing surf...

In this paper, the development of a new methodology for the quantitative determination of the optical absorption coefficient in simple systems in which the light absorption follows Beer's law is described. An approximation of the heat diffusion model of the photoacoustic effect for thermally thick samples is explored. It was found that we could com...

Most photoacoustic (PA) work assumes a point-like detection of generated pressure waves; this assumption results in important differences between predicted and experimental signals, as shown in this paper. We used the geometry of a real sensor in the theoretical signal generation through the discretization of the sensing surface, considering each e...

Here, a new methodology based on the pulsed photoacoustic (PA) technique for real-time monitoring of the ablation process used to synthesize organic nanocrystals is described. The methodology is implemented by ablating microcrystals grown from an organic chromophore with nonlinear optical properties. It was determined that the PA signal from the ab...

A study based on the general solution of the one-dimensional photoacoustic (PA) wave equation for an acoustic plane source is presented. This study relies on obtaining the impulse response of the PA system considering a heating function proportional to the Lambert-Beer law and spatially bounded by a rectangle function. The PA pressure is obtained b...

A photoacoustic model with one degree of freedom in the spatial coordinates for a plane sample is studied. The model proposed considers a sample with Beer's law absorption immersed in a fluid with different acoustical impedance. An analytical solution for this problem is given. It is shown that the generated PA wave is composed of a pressure peak f...

In order to explore the influence of a finite sensor on the detected photoacoustic pressure, we used the solution of the photoacoustic wave equation for a point-like source to simulate the pressure detected by a flat circular sensor. The sensor was simulated by a mesh of point-like sensors connected in parallel. First, we studied the shape of the p...

Preliminary results of an in-plane vibrating system to image objects buried in turbid media are presented. The incident optical beam is vibrated in a periodic back-and-forth motion at low frequency and small constant amplitude in a plane perpendicular to the direction of the beam. The detection is performed in the AC mode, blocking the DC component...

We describe an optical system in which a vibration induced to a laser probe beam combined with a half-blocked photodiode allows determination of the position and width of objects buried in turbid media. Our system is based on the detection of an AC signal which drastically decreases under the presence of an obstructing buried object. We describe th...

An analytical solution for the photoacoustic pressure generated by spherically symmetric objects was obtained by considering decay in the absorbed energy density by unit of time in accordance with Lambert – Beer law. Then the solution was expressed in terms of the Kirchhoff equation. Using the resulting equation, and considering that in biological...

The distinctive spectral absorption characteristics of cancer cells make photoacoustic techniques useful for detection in vitro and in vivo. Here we report on our evaluation of the photoacoustic signal produced by a series of monolayers of different cell lines in vitro. Only the melanoma cell line HS936 produced a detectable photoacoustic signal in...

Based on the pulsed photoacoustic effect, we set up an experimental system to obtain bi–dimensional images of optically–opaque samples embedded within the bulk of turbid medium. The turbid medium was made of agar gel mixed with single–sized nanoparticles; with these materials we induce an optical absorption and an optical scattering like that appea...

During the last decade there has been increased research on breast cancer detection using the pulsed optoacoustic spectroscopy technique (POS), where mostly commercial ultrasonic sensors are used to detect the received signal. However, it has been continually difficult to obtain the correct signal because adequate detectors for this technique have...

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The purpose of this research was to investigate the sensitivity of a system for the detection of circulating melanoma cells based on the thermoelastic properties of melanoma. The method employs photoacoustic (PA) excitation coupled with an optical transducer capable of determining the presence of cells within the circulating system in vitro. The tr...

Circulating tumor cells have been shown to correlate positively with metastatic disease state in patients with advanced cancer. We have demonstrated the ability to detect melanoma cells in a flow system by generating and detecting photoacoustic waves in melanoma cells. This method is similar to flow cytometry, although using photoacoustics rather t...

The open photoacoustic cell technique was used to measure tomato leaves from plants with and without mycorrhizal fungi (Glomus fasciculatum). Based on measurement of the photobaric contribution of the photoacoustic signal, the exponential parameter of the diffusion behavior for this contribution was calculated. From this value, the oxygen diffusion...

The metrological aspects related to the sensitivity and signal-to-noise ratio of the auto-normalized front pyroelectric technique for the measurement of thermal effusivity in liquids are investigated. The effect of the thermally thick approximation in the theoretical expressions for the photopyroelectric signal and its effect on the sensitivity of...

The use of optical spectroscopy as a diagnostic tool in biomedical applications and research has grown considerably in the last two decades. One of them is the pulsed photoacoustic or optoacoustic, which promises to be one of the most important tools for disease diagnostic studies, because while most spectroscopies exploit the optical nature of the...

Pulsed photoacoustic characterization of a human skin phantom with superficial anomalies has been done with a homemade sensor. The sensor was done with a PVDF film and was used in the backward detection mode. The phantoms were agar gelatin slabs with the thickness of 100 mm and superficial anomalies were simulated by plastic spheres immersed in the...

Although some optical spectroscopy methods were introduced more than ten decades ago, they are still finding new applications in many areas of science. Specifically, medicine and biology are two areas of research where optical methods may facilitate and improve the study and characterization of tissue and biological molecules in order to improve me...

In this paper the theory of the differential front photopyroelectric technique is developed. The thermal effusivity measurements of a sample through photopyroelectric direct (no-differential) experiments do not have sufficient resolution and accuracy to detect small changes in the thermal effusivity. To assess minor variations in this thermal magni...

Raman spectroscopy and Multivariate methods were used to study serum blood samples of control and breast cancer patients. Blood samples were obtained from 11 patients and 12 controls from the central region of Mexico. Our results show that principal component analysis is able to discriminate serum sample of breast cancer patients from those of cont...

Raman spectroscopy and Multivariate methods were used to study serum blood samples of control and breast cancer patients. Blood samples were obtained from 11 patients and 12 controls from the central region of Mexico. Our results show that principal component analysis is able to discriminate serum sample of breast cancer patients from those of cont...

. One of the best-known methods to measure the heat capacity of solids consists in the illumination of the sample and the analysis of the thermal relaxation when the illumination is stopped. In this work, the energy balance equation with heat losses due to radiation is solved exactly. This is used to establish the limits of the usual approxima...

ALGUNAS ESPECTROSCOPIAS ÓPTICAS EXISTEN DESDE HACE MÁS DE DIEZ DÉCADAS; SIN EMBARGO, EN RECIENTES AÑOS ESTAS TÉCNICAS SE HAN APLICADO EN DISTINTAS ÁREAS DEL CONOCIMIENTO. POR OTRO LADO, LA MEDICINA Y LA BIOLOGÍA SON DOS ÁREAS DE INVESTIGACIÓN DONDE LA ÓPTICA PUEDE FACILITAR EL ESTUDIO Y CARACTERIZACIÓN DE TEJIDOS Y MOLÉCULAS BIOLÓGICAS CON EL FIN D...

Serum samples were studied using Raman spectroscopy and analyzed through the multivariate statistical methods of principal component analysis (PCA) and linear discriminant analysis (LDA). The blood samples were obtained from 11 patients who were clinically diagnosed with breast cancer and 12 healthy volunteer controls. The PCA allowed us to define...

Laser induced cavitation bubbles in water results from either dielectric breakdown or the fast evaporation due to radiation absorption. The bubbles expand, reach a maximum radius and then supersonically collapse producing a by shock wave. So far, laser induced cavitation has been observed by using short pulsed (femto to nanosecond) lasers. In this...

The prognostic value of exposing malignant melanoma poses an urgent need for an efficient, accurate screening method for metastatic cells. We propose a system for the detection of metastatic tumor cells based upon the thermo-elastic properties of melanoma. The method employs photoacoustic excitation coupled with a detection system capable of exposi...

The prognostic value of exposing malignant melanoma poses an urgent need for an efficient, accurate screening method for metastatic cells. We propose a system for the detection of metastatic tumor cells based upon the thermo-elastic properties of melanoma. The method employs photoacoustic excitation coupled with a detection system capable of exposi...

A brief review of the state of the art in quantitative photoacoustic spectroscopy for thermally thick samples is presented. We demonstrate that it is possible to find an analytical expression that allows studying the optical absorption coefficient by combining the amplitude and phase of the photoacoustic signal, obtained from the heat diffusion mod...

The impedance spectroscopy technique (IST) was used for studying the effect of a 0.5 T magnetic field on the electrical properties of whole human blood. A Solartron SI 1260 spectrometer was used to measure the impedance spectra of magnetic field exposed blood samples compared to non-exposed samples. An equivalent electrical circuit model, consistin...

In the present work, the contribution of the mechanical properties in the coupling of heat diffusion and thermoelastic bending is explored. The analysis of the open photoacoustic cell (OPC) signal for different situations of metal/polymer is presented and discussed.

We report a novel method for measurements in vivo of the penetration of topically applied substances by inverse photopyroelectric configuration. This configuration was used to obtain the thermal effusivity, as a function of time, of in vivo human skin with ointments. This thermal magnitude was employed to characterize the penetration on the anterio...

Mycorrhiza, a common association between root plants and mycorrhizic fungus provides some benefits to the plant, improving its nutrient uptake and increasing the drought resistance as well as the photosynthetic rate. Open photoacoustic (OPC) cell technique was used here to study oxygen evolution from C3 plants (tomato) with and with mycorrhizic fun...

The thermal diffusivity and thermal expansion coefficient of teeth and three of their most common restorative materials (Amalgam Phase Alloy, Ionomer Fuji II LC, and Resin 3MFPITEK Lutine TMZ250) were studied by means of the open photoacoustic technique. These results were then used as a basis for the theoretical simulation of the photothermal proc...

When planning an experiment with the photopyroelectric technique, is necessary to find the correct parameters of the measurement equipment in order to avoid the distortion of the signal in both amplitude and phase. In this work, we present theoretical fundaments for the optimization of the parameters of the electronic equipment of measurement in bo...

We present the theoretical study of the sensitivity of the fotopiroeléctrica technique for back (BPPE) and front (FPPE) configurations, in the voltage mode. The results obtained shown that the BPPE configuration is better for the case in which experimentally the thermal diffusivity is measured. Also, the simulation shows that configuration BPPE is...

A magnetic pulse generator has been set up in order to study gastric activity. Two coils 1.05 m in diameter, arranged in a Helmholtz configuration, were used. The system generated magnetic field pulses higher than 15 mT, of duration 17.3+/-1.2 ms. Measurements were performed in 11 male volunteers, with average age 29.3+/-6.4 years and body mass ind...

The human stomach is a J shaped hollowed organ that undergoes a variable luminal volume without significant pressure changes. This organ has two valves: the cardiac localized in the upper part, and the pillory on the lower part of the organ respectively. The main functions of these valves are to storage, carry, triturate and empty the lumen content...

Twenty measurements of the colon transit time (CTT) were performed by biomagnetic technique in five young women. Subjects were assessed during 12 hours a day for four phases of the menstrual cycle (MC): early follicular (EF), days 1-4 of the MC; late follicular (LF), days 9-14; early luteal (EL), days 15-18; and late luteal (LL), days 23-28 of the...

Implementation of a magnetic stimulator, arranged in a Helmholtz configuration, to study the mechanical activity on human stomachs is presented. In this work, a biomagnetic modality was used, this include swallowed of an oral magnetic contrast made up with 2, 3, 4 or 5 g of ferromagnetic particles diluted in 250 mL of yogurt. After a volunteer had...

Preliminary studies of erythrocyte sedimentation rate in real time, using the inverse photopyroelectric method, are presented. The advantages of this methodology is that the sample is not illuminated directly and that the process can be monitored through the measurement of the thermal contact between a pyroelectric sensor and the blood. The thermal...

This work proposes a new technique for estimation of body composition by using acoustic emission. A simple apparatus for the acoustic emission is proposed.The estimation of the body composition is made by analyzing the correlation between a set of acoustic resonance and skinfold measurements. One device was designed to measure the position and widt...

A simple and low cost experiment is proposed for measuring the earth magnetic field. Results obtained with the system described here are compared to measurements performed using a commercial magnetometer. The value for the earth magnetic field north-south component, Bz = 24.6 ± 0.3 μT, obtained with our system is in good agreement with measurements...

A photoacoustic method for the determination of the heat capacity per unit volume (ρC_p), at room temperature, for thin metallic foils is presented. The method is based on the use of a variant of a conventional photoacoustic cell. © 2003 American Institute of Physics.

The open photoacoustic cell was used to monitor the evolution rate of oxygen from tomato leaves. Estimates of the relative amount of released oxygen in vivo and in situ conditions as influenced by ambient temperature are being presented. Photorespiration phenomenon is shown to dominate above a critical temperature. The evolution of this critical po...

The dynamics of blood and hemolymph sedimentation is studied in real time using the photoacoustic technique. A modified configuration of a conventional photoacoustic cell is used, where the advantage of this methodology is that the sample is not illuminated directly and that the process can be monitored through the measurement of the thermal contac...

Total reflectance attenuated infrared Fourier transform spectroscopy was used to analyze blood samples. Plasma and red blood cells were separated by centrifugation. The spectra were recorded from 200 to 4000 cm-1 under the same conditions for all samples. Samples of healthy donors were compared with those patients with different diseases (polycythe...

A photoacoustic technique is used for studying topically applied substance absorption in human skin. The proposed method utilizes a double-chamber PA cell. The absorption determination was obtained through the measurement of the thermal effusivity of the binary system substance-skin. The theoretical model assumes that the effective thermal effusivi...

This work presents a set of impedance measurements and preliminary results on the analysis of body composition using impedance spectroscopy. This study is made using a pork meat sample and spectra from fat and flesh region were independently obtained using the same electrodes array. From these measurements, and theoretical considerations, it is pos...

The time evolution of the inhomogeneous curing process of polystyrene emulsions is studied using a variant of the conventional photoacoustic (PA) technique. The thermal effusivity, as a function of time, is determined in order to monitor the sintering process of a styrene emulsion in different steps of the manufacturing procedure. PA measuremen...

The collinear mirage technique is widely used to measure the thermal diffusivity of semi-transparent materials. However, in a recent paper [A. Salazar, M. Gateshki and A. Sánchez-Lavega: Appl. Phys. Lett. 76, 2665 (2000)], it was shown that for isotropic materials, because of the influence of photoelastic effect, the method was sensitive to the pol...

Biological systems are able to generate magnetic fields. Despite these fields being so weak, now it is possible to detect them by means of sophisticated equipments, which opens a new research field. Recent studies on this phenomenon reveal that the measurement and analysis of the fields, generated in organs such as the brain, heart, lungs, liver, e...

In this work we propose for the particular problem of penetration of substance into skin, a setup which is based on the conventional photoacoustic cell. In order to avoid some problems, intrinsic to the material under study and the sensibility of the technique, we use the thermal effusivity of the skin-substance system to monitor this phenomenon, i...

In this work, we show a particular setup, which is based on the conventional photoacoustic cell, to measure thermal effusivity of human skin in-vivo and in-situ. We measure the changes of thermal effusivity due to the absorption of sunscreen into the skin and these values are compared with those from an adjacent sample of clean skin. This experimen...

In the semiarid highlands of central Mexico the mesquite tree (Prosopis laevigata) is often removed for agricultural and forestry purposes. Clearing of land for agricultural purposes has a significant impact on soil processes and nutrient dynamics and, ultimately, on crop production. We have studied the effect of the mesquite tree on soil respirati...

In this article, we present a new photoacoustic technique, based on the conventional photoacoustic configuration, to characterize the thermal effusivity of liquid samples. This new technique is applicable for all kind of liquid samples, including the nontransparent ones. In order to show the usefulness of this new technique, we measured the thermal...